Australian Responsible Investors Association chief executive Simon O'Connor said the report highlighted the risks for Australian companies investing in developing countries.

"These allegations, whether proven or not, contain lessons for corporate Australia as to precisely the nature of this new risk landscape and how challenging these risks are to manage," he said.

The banks would not comment on their relationships with companies mentioned in the report but emphasised their commitment to ethical lending practices.

Westpac said it had severed ties with customers that did not meet its ethical guidelines in the past and would do so again if necessary.

"We would continue that same practice if we felt we were representing companies or people that weren't living up to those standards.

ANZ spokesman Stephen Ries said half of the companies linked to it by the report were not customers of the bank and it had reviewed its relationship with others in light of the allegations.

"We asked our customers for updates and we are satisfied with their responses," he said.

But he said the bank would consider the issues raised by Oxfam in its current policy review.

The Commonwealth Bank also said it would review its practices in response to the report, while a NAB spokesman said the bank assessed social and environmental risks before lending to a customer.

The Oxfam report found NAB had lent more than $200 million to Asian palm oil giant Wilmar, which has been linked to land grabs and was named the world's least environmentally friendly company by Newsweek.

ANZ was financing a Cambodian sugar plantation involved in child labour, military backed land grabs and forced evictions, while Westpac has supported a timber company in PNG accused of logging pristine rainforest through an invalid lease arrangement, Oxfam Australia said.